The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of
- A.urea into sulphur dioxide
- B.sugar into carbon dioxide
- C.lipids into methane
- D.urea into ammonia
Correct answer
Explanation
The correct answer is D, urea into ammonia. Bacteria on the floor break down the urea in urine and release ammonia, which has a sharp, pungent smell.
Urea, CO(NH2)2, is the main nitrogenous waste of humans. The liver makes it from ammonia through the ornithine cycle, and the kidneys pass it out in urine. Fresh urine of a healthy person hardly smells. Once it is spilled, bacteria that carry the enzyme urease hydrolyse urea into ammonia and carbon dioxide. The ammonia gas gives stale urine, public toilets and animal sheds their typical odour.
Option A is wrong because urea contains no sulphur, so it cannot give sulphur dioxide. Option B is wrong because the urine of a healthy person contains almost no sugar; sugar in urine is a sign of diabetes, and carbon dioxide is odourless anyway. Option C is wrong because urine has hardly any lipids, and methane too has no smell.
Exam tip: urea + water, with the enzyme urease, gives ammonia + carbon dioxide; the smell of stale urine is ammonia.
Practice Questions
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- B.3, 4
- C.4, 5
- D.3, 5
Show answer
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- D.Ascomycetes, a saprophytic fungi is multicellular or rarely unicellular
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- B.smaller than osmotic pressure
- C.equal to osmotic pressure
- D.equal to atmospheric pressure
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- A.Magnesium
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- A.Liquid nitrogen
- B.Liquid helium
- C.Liquid argon
- D.Liquid bromine
Show answer
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